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Investigation of Highly Concentrated Phenolic Wastewater Treatment in a Membrane Biological Reactor (MBR), and Evaluation of Furfural upon Phenol Biodegradation by an Acclimated Activated Sludge

Mohseni, Mojtaba | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45741 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Borghei, Mehdi
  7. Abstract:
  8. Phenolic compounds are hazardous pollutants that are released into environment through wastewater discharges from variety of industries. Although good biodegradability has been reported at low concentrations, but at higher concentrations phenols are known to be antibacterial. In this study the Membrane Biological Reactor (MBR) with submerged hallow fiber membrane was operated at 25±2 ºC and pH=7.5±0.5 to treat a synthetic wastewater containing high phenol concentration (up to 5.9 g/l). Removal efficiency of phenol and COD were evaluated at four various “Hydraulic Retention Times” (HRT) of 24, 12, 8 and 4 hours. To test the tolerance of the bioreactor to phenol concentration various loading rates were examined. The maximum removal rate of phenol was observed at loading rate of 193 g Phenol-1 g VSS-1 hr-1 while hydraulic retention time was 4 hours and phenol concentration at 5.5g/l. According to COD removal efficiency, there were no significant phenol intermediates in the effluent. That means phenol is degraded by the biomass completely. Microbial community analysis of reactor revealed that two species of bacteria and one specimen of yeast were major components of the reactor microbial culture.High elimination efficiency can be attributed to the activities of these three microbial species that become dominant in the reactor and contribute to the degradation of phenol present in wastewater.This study shows that membrane bioreactor in a suitable system for biological treatment of effluents with high concentrations of phenol. When the acclimated activated sludge could degrade phenol at the rate of 35 g Phenol-1 g VSS-1 hr-1, Kinetics parameters of phenol biodegradation were achieved by using the Haldane equation under batch experiments. Curve fitting data showed that experimental data match Haldane equation in an excellent way (regression is 0.9737). According to presence of furfural in wastewaters and its effect on biomass and efficiency of biodegradation, the impact of furfural upon biodegradation of phenol is also investigated under batch condition. The results show that furfural, which is a toxic compound to microorganisms, has no rigid effect on acclimated biomass, and biomass can degrade furfural along phenol perfectly. In addition, at high phenol concentration, furfural causes a competitive consumption along phenol; as a result, the phenol removal rate was decreased. Growth kinetics of biomass in degradation of furfural is also fitted to The Haldane equation (regression is 0.9843). This study shows that acclimation of biomass plays an important role in biodegradation process, and a well acclimated activated sludge can degrade toxic compounds such phenol and furfural perfectly. Additionally the MBR system is a perfect choice for acclimation of biomass to toxic compounds, and it allows microorganisms to growth slowly without washing out from the reactor
  9. Keywords:
  10. Waste Treatment ; Membrane Bioreactor ; Haldane Equation ; Biodegradation ; Toxic Compound ; Acclimated Activated Sludge

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